1. Field of the Invention
The present invention relates to structural boards with so-called honeycomb structure, and in particular, relates to structural boards used, for example, in vehicles such as automobiles, trains, and airplanes, and in the interiors of buildings.
2. Description of Related Art
Conventionally, as floor structures of office buildings, free-access floors are well known. A free-access floor has multiple pillars positioned in grids on a concrete floor, and a number of flat square panel members of which the four corners thereof are supported by the pillars (for example, see Patent Document 1 below).
The floor member is made of a pure material of low-weight concrete, steel, or plastic. On surfaces of the floor members, finishing members, such as carpets, vinyl tiles, and flooring boards, are placed. The surfaces of the floors are illuminated by fluorescent or incandescent lights at the ceiling.
According to the free-access floors, without degradation of appearances, office equipment and desks can be easily rearranged.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 5-272227
There has been a problem in that when panel members which are designed for the above-mentioned floor structures are used in automobiles and trains, the panel members which are made of pure materials are heavy, and this therefore increases fuel consumption. There has also been a problem in that when the panel members are made thinner in order to reduce fuel consumption, rigidity in trains is not sufficient.
There was a problem in that even with illumination from the ceiling, the feet of passengers were dimly illuminated because of shadows. Even when a passenger dropped something on the floor, it was difficult to find it. Since light from the outside a vehicle is insufficient at night, a similar problem occurs.